Axial exchange currents and the spin content of the nucleon

2003/03/10 by D. Barquilla-Cano, Barquilla-Cano, D., A. J. Buchmann +3
Physics and Astronomy · #FOS: Physical sciences #Nuclear Theory (nucl-th) #nucl-th

paper · pdf · doi:10.48550/arxiv.nucl-th/0303020

30 pages, 3 figures

arxiv created 2003/03/11 · arxiv updated 2009/12/01

Abstract

In a chiral quark model where chiral symmetry is introduced via a non-linear sigma model, we evaluate the axial couplings g_A(0), g_A⁸(0) and g_A⁰(0 )related to the spin structure of the nucleon. Our calculation includes one-body and two-body axial current and pion absorption operators, which satisfy the Partial Conservation of Axial Current (PCAC) condition. While g_A(0) is dominated by the one-body axial current we find significant corrections due to two-body axial exchange currents in g_A⁸(0) and g_A⁰(0). Interestingly, the axial current associated with gluon exchange reduces g_A⁸(0) from 1 to 0.6. Our analysis shows that the so-called ``proton spin crisis'' can be resolved in a constituent quark model in which PCAC is satisfied. Furthermore, we use the PCAC constraint in order to determine the couplings of the eta and eta' mesons to nucleons.

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